U.S. patent number 7,538,050 [Application Number 10/503,546] was granted by the patent office on 2009-05-26 for glass composition.
This patent grant is currently assigned to Nippon Electric Glass Co., Ltd.. Invention is credited to Shigeaki Aoki, Mitsuo Kato, Masataka Takagi, Hachiro Takahashi, Noriyuki Yoshida.
United States Patent |
7,538,050 |
Takagi , et al. |
May 26, 2009 |
**Please see images for:
( Certificate of Correction ) ** |
Glass composition
Abstract
A glass composition of the present invention is manufactured by
melting glass raw materials and contains a multicomponent oxide as
a main component, and the glass composition contains at least one
of helium and neon in an amount of 0.01 to 2 .mu.L/g (0.degree. C.
1 atm).
Inventors: |
Takagi; Masataka (Otsu,
JP), Yoshida; Noriyuki (Otsu, JP),
Takahashi; Hachiro (Otsu, JP), Aoki; Shigeaki
(Otsu, JP), Kato; Mitsuo (Otsu, JP) |
Assignee: |
Nippon Electric Glass Co., Ltd.
(Shiga, JP)
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Family
ID: |
27677855 |
Appl.
No.: |
10/503,546 |
Filed: |
February 5, 2002 |
PCT
Filed: |
February 05, 2002 |
PCT No.: |
PCT/JP03/01185 |
371(c)(1),(2),(4) Date: |
March 28, 2005 |
PCT
Pub. No.: |
WO03/066539 |
PCT
Pub. Date: |
August 14, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050209083 A1 |
Sep 22, 2005 |
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Foreign Application Priority Data
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Feb 5, 2002 [JP] |
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2002-028134 |
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Current U.S.
Class: |
501/27; 501/69;
501/57; 501/43 |
Current CPC
Class: |
C03C
1/004 (20130101); C03C 3/087 (20130101); C03B
5/16 (20130101); C03C 3/091 (20130101); C03C
3/085 (20130101); C03C 3/095 (20130101); C03B
5/193 (20130101); C03C 3/093 (20130101); C03B
5/225 (20130101); C03B 2201/20 (20130101); Y02P
40/57 (20151101) |
Current International
Class: |
C03C
6/00 (20060101); C03C 3/112 (20060101); C03C
3/23 (20060101); C03B 5/16 (20060101); C03B
5/00 (20060101) |
Field of
Search: |
;501/53,27,55-79
;65/32.5,134.1,134.3,134.5,134.9 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0915062 |
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May 1999 |
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EP |
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1184343 |
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Mar 2002 |
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EP |
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1449215 |
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Sep 1976 |
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GB |
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Other References
Article Titled "Hand book of gas diffusion in solids and melts"
1996, ASM International, Materials Park, Ohio, USA. cited by
other.
|
Primary Examiner: Group; Karl E
Assistant Examiner: Wiese; Noah S
Attorney, Agent or Firm: J.C. Patents
Claims
The invention claimed is:
1. A glass composition manufactured by melting glass raw materials
and containing a plurality of oxides as a main component,
characterized by comprising at least one of helium and neon in an
amount of 0.01 to 2 .mu.L/g (0.degree. C., 1 atm).
2. A glass composition according to claim 1, characterized by
comprising a fining component in an amount of 0.001 to 3 mass
%.
3. A glass composition according to claim 1, characterized by
comprising one or more fining components selected from the group
consisting of SO.sub.3, Cl, H.sub.2O, Sn, Sb, F, and As.
4. A glass composition according to claim 1, characterized by
comprising Sb in an amount of 0.01 to 1.5 mass % as
Sb.sub.2O.sub.3.
5. A glass composition according to claim 1, characterized by
comprising SO.sub.3 in an amount of 0.001 to 1.0 mass %.
6. A glass composition according to claim 1, characterized by
comprising Cl in an amount of 0.01 to 1.5 mass %.
7. A glass composition according to claim 1, characterized by
comprising H.sub.2O in an amount of 0.01 to 0.2 mass %.
8. A glass composition according to claim 1, characterized by
comprising Sn in an amount of 5 ppm mass to 2 mass % as
SnO.sub.2.
9. A glass composition according to claim 1, characterized by
comprising As in an amount of 0.01 to 1.5 mass % as
As.sub.2O.sub.3.
10. A glass composition according to claim 1, characterized by
comprising Sb in an amount of 0.01 to 1.5 mass % as
Sb.sub.2O.sub.3, and Sn in an amount of 5 mass ppm to 2 mass % as
SnO.sub.2.
11. A glass composition according to claim 1, characterized by
comprising SO.sub.3 in an amount of 0.001 to 1.0 mass %, and Cl in
an amount of 0.01 to 1.5 mass %.
12. A glass composition according to claim 1, characterized by
comprising Sb in an amount of 0.01 to 1.5 mass % as
Sb.sub.2O.sub.3, and As in an amount of 0.01 to 1.5 mass % as
AS.sub.2O.sub.3.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a glass composition, and more
specifically to a glass composition capable of reducing bubbles in
a glass product by decreasing a dissolved gas in a glass and
capable of improving homogeneity of the glass product.
The most important object among objects addressed over many years
in manufacture of a glass product is to manufacture a very
homogeneous glass by completely removing bubbles remaining in the
glass which lead to defects in the glass product. Various
inventions have been made to attain the object, but a method is not
yet discovered which satisfies the prerequisite of stable
manufacture and supply of a high quality glass demanded by the
industrial world and consumers at low cost and which is easy for
glass manufacturers to implement.
Further, a method of manufacturing a glass product from a solid
such as a method employing a gas phase reaction and a sol-gel
method is recognized. However, in general, the most often employed
industrial method of manufacturing a large amount of a glass
product involves: using a mixture of inorganic compounds as a main
raw material for glass raw materials; and melting the raw materials
at high temperatures, to manufacture a glass product. According to
the manufacturing method employing melting, methods of removing
bubbles from a molten glass are roughly classified into a chemical
method and a physical method. A typical example of the former
method is a method of adding fining agents into glass raw
materials, and a typical example of the latter method is a method
of reducing pressure or vacuum degassing the molten glass.
In particular, while a wide variety of glass products are supplied
recently, the former method generally involves: adding a minute
amount of fining agents into the glass raw materials; heating the
glass raw materials at high temperatures for foaming in a molten
glass through their decomposition or redox reaction; and removing a
carbon dioxide gas generated during melting, bubbles remaining in
the raw materials, nitrogen generated during glass melting. The
method is characterized in that, although attention must be focused
on control of glass melting temperature and of molten glass flow
and on segregation of fining agents in the glass raw materials, the
method enables continuous mass production of a glass product with
relative ease if a fining agent providing a stable fining effect
can be selected. There exist many cases where such a fining method
suitable for mass production of glass has been employed during
melting.
Among those, the most frequently employed method involves adding
arsenic, which provides a sufficient fining effect with minute
addition, as oxide in the glass. However, environmental problems
have been pointed out regarding addition of arsenic. Thus, an
urgent need of selecting another fining agent for replacing arsenic
or for reducing the amount of arsenic added as a fining agent has
resulted in reexamination of other hitherto proposed fining agents,
developments of new fining compounds, or the like. Among those,
many substances such as antimony, chlorine, and niter have been
studied as substitute for arsenic, but a fining agent having a
fining effect surpassing that of arsenic is far from found,
particularly for an oxide glass requiring high temperature melting.
Thus, melting furnace conditions have been studied for aiding the
fining effect of the fining agent replacing arsenic, and many
attempts have been made on various measures for solving the
problems such as combination of a plurality of fining agents and
increase of furnace temperature. However, despite such continuous
studies and attempts, a low-cost method applicable to various glass
compositions and assuredly providing a stable and good fining
effect is not yet found.
On the other hand, examples of the physical method include:
reduction of glass viscosity by increasing a melting temperature; a
centrifugal method; flow control of molten glass inside the
furnace; a stirring method; a gas blowing method; a
sonic/ultrasonic method; an reduced pressure method; control of a
melting atmosphere; and a combination thereof. Several inventions
have been reported regarding a method of forcibly accelerating a
rise of bubbles in the glass to the surface by keeping the molten
glass under reduced pressure, for example. Patent Document 1 and
Patent Document 2 below each describe a reduced pressure defoaming
apparatus arranged between a melting tank and a working tank of a
glass melting furnace. However, such methods are not yet widely
used as a general method of homogenizing a glass because the
methods are not as easy as the chemical method to implement, do not
provide comparable results as those of the chemical method, require
a very large capital investment, and limit a usable glass
composition.
Various gases are employed for a melting atmosphere in a part of a
glass manufacturing process. Among those, Patent Document 3 below
describes a method involving remelting a glass in an inert gas
atmosphere as a means for preventing reboiling. Further, Patent
Document 4 below describes use of a hydrogen gas or a helium gas
during a densing process of a quarts glass tube base material.
Further, Patent Document 5 below describes reduction of a water
content in a glass by bubbling a gas selected from the group
consisting of C0.sub.2, N.sub.2, O.sub.2, NO.sub.x, and a noble gas
as a dry gas.
Further, Patent Document 6below describes that a supplemental
effect can be realized during fining of a molten glass by using
helium with sodium chloride, and that the effect was confirmed upon
using helium with a very small, experimental amount of the molten
glass.
Patent Document 1: JP 11-130442 A (p. 2-7, FIGS. 1-2)
Patent Document 2: JP 11-130444 A (P. 2-7, FIG. 1)
Patent Document 3: JP 06-329422 A (p. 2-4)
Patent Document 4: JP 09-301726 A (p. 2-4, FIG. 1)
Patent Document 5: JP 07-172862 A (p. 2-8, FIGS. 1-7)
Patent Document 6: U.S. Pat. No. 3,622,296
Defoaming of a molten glass under reduced pressure as in Patent
Document 1 and Patent Document 2 may be recognized as one measure,
but such a method requires large-scale remodeling of a
manufacturing facility and may require introduction of an expensive
devices, thereby being disadvantageous to attain a reduced cost
price for manufacture of a glass product requiring mass
production.
Further, adoption of the inert gas for the melting atmosphere as in
Patent Document 3 and Patent Document 4 has been realized for
specific glass compositions. However, the method is for shielding
the molten glass from oxygen and for adjusting the water content.
Neither Patent Document 3 nor Patent Document 4 describes an inert
gas content in the glass or a fining action during glass
melting.
On the other hand, a fining method in Patent Document 6 had focused
on the helium gas for the first time, and was an innovative fining
method for the molten glass. However, the method was regarded
supplemental to specific glass compositions, and assumes nothing on
quantitative criteria of helium usage for broader applications,
applications to glass materials of other grades, or the like. Thus,
no follower of the method appeared, resulting in no application of
the method to a widely used multicomponent oxide glass and no new
improvements.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel glass
composition capable of fundamentally solving problems in fining of
a multicomponent oxide glass during melting.
The inventors of the present invention have found, through studies
on conventional fining of a multicomponent oxide glass during
melting, an optimum glass composition applicable to various uses by
including helium and/or neon in a wide variety of multicomponent
oxide glass products manufactured by high temperature melting.
That is, a glass composition according to the present invention
relates to a glass composition manufactured by melting glass raw
materials and containing a plurality of oxides as main components,
characterized by including at least one of helium and neon in an
amount of 0.01 to 2 .mu.L (micro liters)/g (0.degree. C., 1
atm).
The inventors of the present invention have found that bubbles in
the molten glass can be removed completely or can be drastically
reduced, thus providing a good fining effect, by including as a
component providing a fining effect to the molten multicomponent
oxide glass, a predetermined amount of helium or neon as an inert
gas component.
Each element in the molten glass is generally in a network state
having a weak bonding force, and higher temperatures cause
vigorous, irregular element position changes involving stretching
vibration, rotation vibration, and bending vibration at a
relatively high speed. However, as described below, helium and neon
have very low reactivities and are small because an electron
arrangement of each atomic structure has a closed shell structure.
Thus, helium or neon hardly bonds with various elements
constituting a molten glass, and are sufficiently small to pass
through openings of a vibrating network. Therefore helium or neon
can easily diffuse through the molten glass without being affected
by surrounding elements.
Thus, when the molten glass is brought into contact with a helium
and/or neon gas to dissolve helium and/or neon in the molten glass,
the gas of helium or neon follows the Henry's law and rapidly
diffuses to a predetermined partial pressure in the molten glass.
On the other hand, oxygen, carbon dioxide, water vapor,
sulfurdioxide, halogen, or the like in the molten glass have a
smaller diffusion rate than that of helium or neon, and do not
permeate through the molten glass at the same rate as the diffusion
rate of helium or neon into the molten glass. Thus, the total
partial pressure in the molten glass increases.
Oxygen, carbon dioxide, steam, sulfur dioxide, halogen, or the like
generates through a chemical reaction or the like of the glass raw
materials. An absence of a fining agent results in the total
partial pressure in the molten glass exceeding an external
pressure, that is, exceeding 1 atm in the atmosphere through the
diffusion of helium or neon. Helium and neon function as follows
under such high pressure conditions. That is, an amount of a gas
such as oxygen, carbon dioxide, and water vapor dissolved in the
molten glass is represented as a partial pressure in the molten
glass. When the total partial pressure exceeds the external
pressure of 1 atm, the gas such as oxygen, carbon dioxide, water
vapor, sulfur dioxide, and halogen hardly remains stably dissolved
in the glass, and diffuses into fine bubbles present in the
surroundings. As a result, bubble sizes expand in the molten glass
and the bubbles increase in rising rate and disappear at a glass
surface, to thereby remove fine bubbles in the molten glass.
Further, when the molten glass contains a fining agent added to raw
materials, an amount of an oxygen gas in the molten glass, that is,
an oxygen partial pressure remains at equilibrium with redox
reaction of a fining agent. As described above, the oxygen gas at
equilibrium diffuses into fine bubbles by dissolution of helium or
neon in the molten glass, and a partial pressure of oxygen
equilibrium with the fining agent established in the molten glass
is ruined. Thus, the reduction of fining agent is promoted, to
supply oxygen gas in the molten glass. As a result, dissolution of
helium or neon in the molten glass enables efficient supply of
oxygen gas from the fining agent in the molten glass, which is the
most effective fining gas in oxide glasses.
As described above, two steps involved in the dissolution of helium
or neon in the molten glass can assuredly realize further promotion
of decomposition of a fining agent added as a raw material in the
molten glass during homogenization of the molten glass having a
composition of the present invention maintained at high
temperatures. That is, the two steps involve: 1) increasing the
total pressure of gases to realize a high pressure state necessary
for discharge of gases from the molten glass; and 2) forming
bubbles as a gas phase from a dissolved gas phase with high
pressure such as oxygen, or promoting bubble expansion, in the
molten glass.
Both helium and neon used in the present invention may be
classified as inert gases and noble gases, and have stable closed
shell structures to exist as monoatomic molecules. Helium is the
lightest element among the noble gas elements, and is also very
small structurally. Helium has a very small attracting force by the
Van der Waals force, and thus, helium does not solidify and remains
liquid even at the absolute temperature of zero under normal
atmospheric pressure. Further, neon is the second smallest element
next to helium among the noble gas elements and has a stable
structure as a monoatomic molecule. Thus, both helium and neon are
captured in voids of a glass network structure that consists of
inorganic oxides in the glass product cooled after high temperature
melting.
Helium or neon is not involved in network structure formation of
the glass, but inclusion thereof alone or in total in an amount of
0.01 .mu.L/g or more in the glass provides a fining effect to the
molten glass and provides a homogeneous glass. A content of less
than 0.01 .mu.L/g cannot provide a sufficient fining effect. For an
assured fining effect, a content is preferably 0.06 .mu.L/g or
more. A content is more preferably 0.1 .mu.L/g or more. Such a
content can realize a sufficient clarifying effect even under harsh
conditions including a large content of gasifying components in the
glass. On the other hand, a content exceeding 2 .mu.L/g is not
preferable because so-called reboiling, that is, re-foaming occurs
through reheating of the glass composition. A preferable upper
limit of the content is 1.5 .mu.L/g (1.5 .mu.L/g or less) for
inhibiting reboiling, though varying depending on the glass
composition, heating conditions, or the like. The preferable upper
limit of the content is 1.0 .mu.L/g (1.0 .mu.L/g or less) for a
glass composition in which a fining agent except helium or neon
coexists, because reboiling tends to occur more easily.
Thus, a preferable range of a helium and/or neon content is 0.1
.mu.L/g to 1.5 .mu.L/g in the molten glass, in which no fining
agent except helium or neon coexists, for providing a fining agent
effect under harsher conditions and for inhibiting reboiling. On
the other hand, a preferable range of the helium and/or neon
content in the molten glass, in which a fining agent except helium
or neon coexists, is 0.1 .mu.L/g to 1.0 .mu.L/g, for providing a
fining effect under harsher conditions and for inhibiting
reboiling.
Further, a glass formation path includes formation from a gas chase
through vaporization or formation from a solid phase through a
sol-gel method, but the present invention is intended for a glass
formed by retaining the glass raw materials at high temperatures
and cooling the molten glass. Energy for melting glass raw
materials may be provided through: burning of a solid, liquid, or
gas fuel; electromagnetic radiation such as electricity and
infrared radiation; and radiation heat or conductive heat from
other high temperature media.
A glass composition of the present invention is manufactured by
melting glass raw materials. That is, the glass raw materials are
precursors before melting and are substances which vitrify as
so-called an super cooled liquid by heating to high temperatures
once and then cooling. The glass raw materials solidify into a
glass composition of a product containing a plurality of oxides as
main components. The glass raw materials are not limited as long as
a glass phase coexists in the glass composition even if a crystal
phase forms on a surface and inside thereof by the presence of the
surface, an interface, or the like depending on the cooling
procedures and cooling conditions employed.
That is, examples of the glass raw materials that can be used in
the present invention include materials containing: a single
substance, a mixture, or a compound of inorganic substances such as
oxides, carbonates, phosphates, chlorides, and various glass as a
main component; and a single substance, a mixture, or a compound of
organic additives, metal additives, or the like as an additive, if
required. As represented by a classification of the glass based on
source of the glass raw materials, any substance such as natural
products, synthetic products, or purified products may be used as
long as it provides necessary components for a glass composition
that contains a plurality of oxides as main components. Further,
highly purified industrial products, with impurities in a ppm order
or a ppb order removed through various methods, can be employed as
glass raw materials of the present invention. Further, generally
used raw materials for glass manufacture, manufactured and purified
in mining and chemical industries, may also be used as raw
materials for the glass composition of the present invention.
The phrase "glass composition containing a plurality of oxides as
main components" as used in the present invention refers to a glass
composition containing two or more types of oxides and containing
50 mass % or more of the two or more types of oxides in total. The
"glass composition containing a plurality of oxides as main
components" of the present invention does not apply to a glass
composition having a single composition with a plurality of oxide
components mixed as impurities, for example. To be specific, the
"glass composition containing a plurality of oxides as main
components" of the present invention does not apply to a glass
composition containing close to 99% in mass % of a single component
and 0.09 mass % or less, that is, two decimal places, of the
plurality of oxide components respectively, for example.
Further, melting of the glass raw materials generally involves:
collectively holding the glass raw materials in a vessel; and then
melting the materials while preventing the plurality of raw
materials from separating during high-temperature heating. A method
which may also be employed as appropriate involves: applying an
external force such as gas flow pressure and electromagnetic force;
and floating to melt. Further, a medium having a function of
holding the raw materials and maintaining them at high temperatures
can be used for melting the glass raw materials even if the medium
does not serve as a vessel. Thus, the medium does not have to be
necessarily a solid, and may be a liquid such as liquid metal
containing a single or a plurality of components.
While a vessel hardly reacting with the glass raw materials during
melting is preferably selected when using a vessel for melting, any
material, whether it is a metal or inorganic substance, may be used
as a material constituting the vessel for applications where some
amount of impurities may be allowed to be mixed in the glass
composition. Further, when a vessel is used for capturing glass raw
materials in aerospace or in a space simulating aerospace where no
gravity acts, and if wettability between the vessel and the glass
is too high, the glass flows over a vessel wall to the outside.
Thus, wettability also must be considered. Industrial materials
generally used in glass industries and exhibiting heat resistance
as a main property, so-called refractories, can be employed alone
or in a mixture for the vessel.
Further, examples of methods of adding helium or neon to the glass
composition of the present invention include: a method involving
retaining glass raw materials in a helium or neon atmosphere before
melting and gradually increasing temperature in the same atmosphere
while maintaining this state, for melting the glass raw materials;
and a method involving sufficiently melting glass raw materials and
then bringing the molten glass into contact with helium or neon,
for diffusing helium or neon in the molten glass. Alternatively,
use of raw materials or glass cullet having high helium or neon
concentration for a specific raw material species in the glass raw
materials enables effective addition of helium or neon into the
glass composition.
Further, a method of diffusing helium or neon in the molten glass
by adjusting an atmosphere surrounding the glass to a helium or
neon atmosphere is an easy method of adding helium or neon. Other
methods thereof include: a method of bubbling helium or neon in the
molten glass using a refractory nozzle; and a method of employing
as a material constituting a vessel, a refractory material having
pores allowing diffusion of helium or neon, and generating many
fine helium or neon bubbles from a bottom of the vessel, for
efficient diffusion. Further, a porous refractory tip of a
refractory nozzle immersed in the vessel can provide low cost and
efficient diffusion of helium or neon.
Further, a glass composition of the present invention may contain a
fining component in an amount of 0.001 to 3 mass %, in addition to
the above composition (composition described in claim 1).
According to the present invention, a fining agent may include: a
substance which has a high vapor pressure during high temperature
heating, heat decomposing, and melting of the glass raw materials,
which gasifies and separates from the molten glass, and which
partially contains a melting atmosphere gas captured in the raw
materials during melting of glass raw materials. The fining agent
generally refers to a chemical substance serving to form a
homogeneous molten glass by releasing a gas mixture perceived as
bubbles in the molten glass. Specific examples of a gas forming
bubbles in the molten glass include CO.sub.2, SO.sub.2, O.sub.2,
N.sub.2, H.sub.2O, H.sub.2, Ar, and a mixture gas thereof. At high
temperatures, an evaporated or vaporized substance from the molten
glass may be included in a minute amount as a gas component.
Examples of various compounds, elements, and mixtures that can be
used as the fining agent include: arsenic compounds such as
As.sub.2O.sub.3; antimony compounds such as Sb.sub.2O.sub.3,
2MgO.Sb.sub.2O.sub.5, 7MgO.Sb.sub.2O.sub.5, 2ZnO.Sb.sub.2O.sub.5,
7ZnO.Sb.sub.2O.sub.5, 3CaO.Sb.sub.2O.sub.5, 6CaO.Sb.sub.2O.sub.5,
2SrO.Sb .sub.2O.sub.5, 6SrO.Sb.sub.2O.sub.5, BaO.Sb.sub.2O.sub.5,
4BaO.Sb.sub.2O.sub.5, Li.sub.2O.Sb.sub.2O.sub.5,
2Li.sub.2O.Sb.sub.2O.sub.5, K.sub.2O.Sb.sub.2 O.sub.5, LaSbO.sub.4,
SbNbO.sub.5, Sr(Ca.sub.0.33Sb.sub.0.67)O.sub.3, LiZnSbO.sub.4,
Li.sub.1.5Ti.sub.1.0Sb.sub.0.5O.sub.4,
Ba.sub.2Al.sub.0.5Sb.sub.0.5O.sub.6, Ba.sub.2Ce.sub.0.75SbO.sub.6,
ZrSbPO.sub.7, Ba (Sb.sub.0.5Sn.sub.0.5)O.sub.3, LiSiSbO.sub.5, and
Li.sub.2Zr.sub.2Sb.sub.2SiO.sub.11; oxides such as SnO.sub.2,
CeO.sub.2, and BaO.sub.2; peroxides; nitrates such as NaNO.sub.3,
KNO.sub.3, and Ba(NO.sub.3).sub.2; sulfates such as
Na.sub.2SO.sub.4, K.sub.2SO.sub.4, CaSO.sub.4, and BaSO.sub.4;
chlorides such as NaCl, KCl, and CaCl.sub.2; fluorides such as
CaF.sub.2, Na.sub.2SiF.sub.6, LiF.KF.Al.sub.2O.sub.3. 3SiO.sub.2,
and KF metal and inorganic elements such as Al, Si, Zn, Ga, Fe, Sn,
and C; H.sub.2O; Al(OH).sub.3; and organic compounds that are
carbon-containing compounds such as sucrose, granulated sugar,
cornstarch, and wood powder.
A fining component content, though varying depending on type
thereof and the glass composition used, is preferably 0.001 mass %
or more for providing a fining effect to the molten glass in
coexistence with helium or neon. Further, the fining component
content is more preferably 0.01 mass % or more for a significant
fining effect. Further, for a glass composition hardly diffusing
helium or neon, the fining component content is preferably 0.03
mass % or more. On the other hand, a fining component content
exceeding 3 mass % poses problems of excessive gas generation and
difficulty of removal of the bubbles from the molten glass. An
upper limit of the fining component content is preferably 2.5 mass
% for a glass product under harsh conditions for inhibiting foaming
during reheat treatment, and more preferably 2.0 mass % for a glass
composition applied to a glass product used under harsher
conditions. Thus, a preferable fining component content ranges from
0.01 to 2.5 mass %, and optionally 0.01 to 2 mass %, 0.03 to 2.5
mass %, 0.03 to 2 mass %, 0.01 to 3 mass %, and 0.03 to 3 mass
%.
Further, an addition method for the fining component is not
particularly limited, and the fining component may be added as a
melting raw material component or may be added to the molten glass.
The fining component can be added simultaneously with the addition
of helium or neon. Further, the fining component can be added to
the glass intentionally as an elution component eluting from a
vessel and a refractory material immersed in the molten glass. The
fining component can be added alternatively with helium or neon.
The addition amount of the fining component can be adjusted to an
optimum amount by gradually increasing or decreasing the addition
amount while the fining effect is confirmed.
A helium and/or neon content is preferably 0.1 to 1.0 .mu.L/g when
helium and/or neon is coexistent with the fining component.
Further, a glass composition of the present invention may contain
as a fining component one or more components selected from the
group consisting of SO.sub.3, Cl, H.sub.2O, Sn, Sb, F, and As, in
addition to the above composition (composition described in claim
1).
SO.sub.3, Cl, H.sub.2O, Sn, Sb, F, or As as defined herein as a
fining component exhibits a good fining effect among the various
fining agents when coexisting with helium and/or neon, and is a
component which partially remains in a cooled glass component even
after modification through heat decomposition by high temperature
melting and through a redox reaction.
Further, a glass composition according to the present invention may
contain Sb in an amount of 0.01 to 1.5 mass % as Sb.sub.2O.sub.3,
in addition to the above composition (composition described in
claim 1).
Sb (antimony) is a component serving as a fining agent in the glass
composition, and exhibits a good fining effect when coexisting with
helium and/or neon. However, an Sb.sub.2O.sub.3 content of less
than 0.01 mass % in the glass composition cannot provide a
sufficient effect. Thus, the Sb.sub.2O.sub.3 content must be 0.01
mass % or more. The Sb.sub.2O.sub.3 content is preferably 0.1 mass
% or more for a better effect. On the other hand, the
Sb.sub.2O.sub.3 content must be 1.5 mass % or less because an
Sb.sub.2O.sub.3 content exceeding 1.5 mass % poses a problem of
reboiling by heat treatment during fabrication. Further, the
Sb.sub.2O.sub.3 content is preferably 1.0 mass % or less,
particularly if high temperature heat treatment is employed during
fabrication, because stability against reboiling further increases
with the Sb.sub.2O.sub.3 content of 1.0 mass % or less. The
Sb.sub.2O.sub.3 content is preferably 0.7 mass % or less when
another gas component possibly causing reboiling coexists.
Further, a glass composition according to the present invention may
contain SO.sub.3 in an amount of 0.001 to 1.0 mass %, in addition
to the above composition (composition described in claim 1).
SO.sub.3 is a component serving as a fining agent in the glass
composition, and provides an enhanced fining effect for bubbles in
the molten glass when coexisting with helium and/or neon. However,
an SO.sub.3 content of less than 0.001 mass % in the glass
composition cannot provide a sufficient fining effect. Thus, the
SO.sub.3 content must be 0.001 mass % or more. The SO.sub.3 content
is preferably 0.01 mass % or more for realizing a better effect.
The SO.sub.3 content is preferably 0.03 mass % or more for
realizing a sufficient fining effect under harsh conditions. On the
other hand, the SO.sub.3 content must be 1.0 mass % or less because
an SO.sub.3 content exceeding 1.0 mass % poses a problem of easy
generation of bubbles through reboiling by reheat treatment during
fabrication after cooling. A safer SO.sub.3 content, though varying
depending on reheat treatment conditions, is 0.8 mass % or less.
The SO.sub.3 content is preferably 0.5 mass % or less when another
gas component possibly causing reboiling coexists.
Further, a glass composition according to the present invention may
contain Cl in an amount of 0.01 to 1.5 mass %, in addition to the
above composition (composition described in claim 1).
Cl (chlorine) is a component which exhibits a fining effect of
promoting vaporization of a gas component from the molten glass
when coexisting with helium and/or neon. However, a Cl content of
less than 0.01 mass % in the glass composition cannot provide a
sufficient fining effect. Thus, the Cl content must be 0.01 mass %
or more. The Cl content is preferably 0.03 mass % or more for
realizing a better fining effect. On the other hand, the Cl content
must be 1.5 mass % or less because a Cl content exceeding 1.5 mass
% poses a problem of readily impairing chemical resistance of the
glass and provides a glass composition without practically
sufficient resistance. An upper limit of the Cl content is
preferably 1.2 mass % for a glass composition requiring higher
chemical resistance and weatherability. The upper limit of the Cl
content is preferably 1.0 mass % when another component
deteriorating the chemical resistance and weatherability
coexists.
Further, the following facts have been found about F which is a
halogen gas like Cl. F has an effect of promoting vaporization of a
gas component from the molten glass and of reducing a glass
viscosity during melting when coexisting with helium and/or neon,
and thus, inclusion of a predetermined amount of F in the glass
composition is effective for attaining the intended effect of the
present invention. In that case, an F content preferably ranges
from 0.01 to 2.0 mass %. The F content of less than 0.01 mass %
cannot provide a sufficient effect. The F content is preferably
0.03 mass % or more for realizing a better effect. On the other
hand, the F content preferably does not exceed 2.0 mass % in the
glass composition because F deteriorates the chemical resistance of
the glass similarly to Cl by bonding with cation components in the
glass to break a glass network structure in a cooled glass. An
upper limit of the F content is preferably 1.5 mass % for a glass
composition requiring higher chemical resistance. The upper limit
of the F content is preferably 1.0 mass % when another component
deteriorating the chemical resistance coexists.
Further, a glass composition according to the present invention may
contain H.sub.2O in an amount of 0.01 to 0.2 mass %, in addition to
the above composition (composition described in claim 1).
H.sub.2O is an effective component since it exhibits an effect of
reducing a glass viscosity and of promoting discharge of a gas
component from the molten glass when coexisting with helium and/or
neon. However, an H.sub.2O content of less than 0.01 mass % in the
glass composition cannot provide a sufficient effect. Thus, the
H.sub.2O content is preferably 0.01 mass % or more. The H.sub.2O
content must be 0.03 mass % or more for a better gas component
vaporization effect. On the other hand, the H.sub.2O content
preferably does not exceed 0.2 mass % in the glass composition
because H.sub.2O deteriorates the chemical resistance and
weatherability of the glass by bonding with other cations in the
glass to break a glass network structure in a cooled glass.
Further, the H.sub.2O content is preferably 0.15 mass % or less
when another component deteriorating the chemical resistance and
weatherability coexists. Further, the H.sub.2O content is
preferably 0.10 mass % or less for a glass product requiring,
particularly, the chemical resistance and weatherability.
Further, a glass composition according to the present invention may
contain Sn in an amount of 5 mass ppm (that is, 5.times.10.sup.-4
mass %) to 2 mass % as SnO.sub.2, in addition to the above
composition (composition described in claim 1).
Sn (tin) is a component serving as a fining agent in the glass
composition, and exhibits a good fining effect when coexisting with
helium and/or neon. However, an SnO.sub.2 content of less than 5
mass ppm in the glass composition cannot provide a sufficient
effect. Thus, the SnO.sub.2 content must be 5 mass ppm or more. The
SnO.sub.2 content is preferably 100 mass ppm or more for exhibiting
an assured effect with a small helium and/or neon content in the
glass composition. The SnO.sub.2 content is preferably 0.05 mass %
or more, that is, 500 mass ppm or more, for a better effect with a
glass composition requiring high temperature melting. On the other
hand, the SnO.sub.2 content is preferably 2 mass % or less because
an SnO.sub.2 content exceeding 2 mass % poses a problem of
reboiling by heating in applications requiring heat treatment
during fabrication. Further, the SnO.sub.2 content is preferably
1.5 mass % or less for enhancing stability against reboiling, and
is preferably 1.2 mass % or less, if high temperature heat
treatment is employed during fabrication. The SnO.sub.2 content is
preferably 0.7 mass % or less when another reboil gas component
coexists.
Further, a glass composition according to the present invention may
contain As in an amount of 0.01 to 1.5 mass % as As.sub.2O.sub.3,
in addition to the above composition (composition described in
claim 1).
As (arsenic) is a component serving as a fining agent in the glass
composition as Sb, and exhibits a good fining effect when
coexisting with helium and/or neon. However, an As.sub.2O.sub.3
content of less than 0.01 mass % in the glass composition cannot
provide a sufficient effect. Thus, the As.sub.2O.sub.3 content must
be 0.01 mass % or more for a better effect. On the other hand, the
As.sub.2O.sub.3 content must be 1.5 mass % or less because an
As.sub.2O.sub.3 content exceeding 1.5 mass % poses a problem of
reboiling by heat treatment during fabrication. Further, the
As.sub.2O.sub.3 content is preferably 1.0 mass % or less,
particularly if high temperature heat treatment is employed during
fabrication, because stability against reboiling further increases
with the As.sub.2O.sub.3 content of 1.0 mass % or less. The
As.sub.2O.sub.3 content is preferably 0.7 mass % or less when
another reboil gas component coexists.
Further, a glass composition according to the present invention may
contain Sb in an amount of 0.01 to 1.5 mass % as Sb.sub.2O.sub.3
and Sn in an amount of 5 mass ppm to 2 mass % as SnO.sub.2, in
addition to the above composition (composition described in claim
1).
Sb and Sn here respectively have the above-described effects
separately, and a glass composition containing both elements may
exhibit even better effects. When Sb and Sn coexist, an
Sb.sub.2O.sub.3content of less than 0.01 mass % as Sb cannot
provide a sufficient effect. Thus, the Sb.sub.2O.sub.3 content must
be 0.01 mass % or more. The Sb.sub.2O.sub.3 content is preferably
0.08 mass % or more for a better effect. On the other hand, the
Sb.sub.2O.sub.3 content must be 1.5 mass % or less because an
Sb.sub.2O.sub.3 content exceeding 1.5 mass % poses a problem of
reboiling by heat treatment during fabrication. Further, the
Sb.sub.2O.sub.3 content is preferably 0.8 mass % or less,
particularly if high temperature heat treatment is employed during
fabrication, because stability against reboiling further increases
with the Sb.sub.2O.sub.3 content of 0.9 mass % or less. The
Sb.sub.2O.sub.3 content is preferably 0.6 mass % or less when
another gas component possibly causing reboiling coexists.
An SnO.sub.2 content of less than 5 mass ppm as Sn cannot provide a
sufficient effect. Thus, the SnO.sub.2 content must be 5 mass ppm
or more. The SnO.sub.2 content is preferably 80 mass ppm or more
for exhibiting an assured effect with a small helium and/or neon
content in the glass composition. The SnO.sub.2 content is
preferably 0.04 mass % or more, that is, 400 mass ppm or more for
better effects with a glass composition requiring high temperature
melting. On the other hand, the SnO.sub.2 content must be 2 mass %
or less because an SnO.sub.2 content exceeding 2 mass % poses a
problem of reboiling by heating in applications requiring heat
treatment during fabrication. Further, the SnO.sub.2 content is
preferably 1.4 mass % or less for enhancing stability against
reboiling, and is preferably 1.1 mass % or less, if high
temperature heat treatment is employed during fabrication. The SnO2
content is preferably 0.6 mass % or less when another reboil gas
component coexists.
Further, a glass composition according to the present invention may
contain SO.sub.3 in an amount of 0.001 to 1.0 mass % and Cl in an
amount of 0.01 to 1.5 mass %, in addition to the above composition
(composition described in claim 1).
SO.sub.3 and Cl here respectively have the above-described effects
separately, and a glass composition containing both elements can
exhibit even better effects compared to that containing a single
element. The combination of SO.sub.3 and Cl is effective in melting
of a glass composition having a high viscosity, which is hardly
fined. However, an SO.sub.3 content of less than 0.001 mass % in
the glass composition cannot provide a sufficient effect. Thus, the
SO.sub.3 content must be 0.001 mass % or more, preferably 0. 005
mass % or more. The SO.sub.3 content is preferably 0.01 mass % or
more for realizing deaeration under harsher conditions. On the
other hand, the SO.sub.3 content is preferably 1.0 mass % or less
because an SO.sub.3 content exceeding 1.0 mass % poses a problem of
easy generation of bubbles through reboiling by reheat treatment
during fabrication after cooling. An upper limit of a safer
SO.sub.3 content, though varying depending on reheat treatment
conditions, is 0.7 mass %. The SO.sub.3 content is preferably 0.4
mass % or less when another gas component possibly causing
reboiling coexists.
A Cl content of less than 0.01 mass % in the glass composition
cannot provide a sufficient fining effect, when SO.sub.3 and Cl
coexist. Thus, the Cl content must be 0.01 mass % or more. The Cl
content is preferably more than 0.02 mass % for realizing a better
clarifying effect. On the other hand, an upper limit of the Cl
content must be 1.5 mass % because a Cl content exceeding 1.5 mass
% poses a problem of readily impairing chemical resistance of the
glass and provides a glass composition without practically
sufficient resistance. The upper limit of the Cl content is
preferably 1.1 mass % for a glass composition used in applications
requiring higher chemical resistance and weatherability. The upper
limit of the Cl content is preferably 0.9 mass % when another
component deteriorating the chemical resistance and weatherability
coexists.
Further, a glass composition according to the present invention may
contain Sb in an amount of 0.01 to 1.5 mass % as Sb.sub.2O.sub.3
and As in an amount of 0.01 to 1.5 mass % as As.sub.2O.sub.3, in
addition to the above composition (composition described in claim
1).
Sb and As here respectively have the above-described effects
separately, and a glass composition containing both elements can
exhibit better effects in a broader temperature range compared to
that containing a single element because of different decomposition
temperatures of oxides. However, an Sb.sub.2O.sub.3 content of less
than 0.01 mass % in the glass composition cannot provide a
sufficient effect. Thus, the Sb.sub.2O.sub.3 content must be 0.01
mass % or more. The Sb.sub.2O.sub.3 content is preferably 0.07 mass
% or more for a better effect. On the other hand, the
Sb.sub.2O.sub.3 content is preferably 1.5 mass % or less because an
Sb.sub.2O.sub.3 content exceeding 1.5 mass % poses a problem of
reboiling by heat treatment during fabrication. Further, the
Sb.sub.2O.sub.3 content is preferably 0.9 mass % or less,
particularly if high temperature heat treatment is employed during
fabrication, because stability against reboiling further increases
with the Sb.sub.2O.sub.3 content of 0.9 mass % or less. The
Sb.sub.2O.sub.3 content is preferably 0.7 mass % or less when
another gas component possibly causing reboiling coexists.
An As.sub.2O.sub.3 content of less than 0.01 mass % as As in the
glass composition cannot provide a sufficient effect, when
Sb.sub.2O.sub.3 and As.sub.2O.sub.03 coexist. Thus, the
As.sub.2O.sub.3 content must be 0.01 mass % or more. The
As.sub.2O.sub.3 content is preferably 0.02 mass % or more for
realizing a better effect. On the other hand, the As.sub.2O.sub.3
content must be 1.5 mass % or less because an As.sub.2O.sub.3
content exceeding 1.5 mass % poses a problem of reboiling by heat
treatment during fabrication. Further, the As.sub.2O.sub.3 content
is preferably 0.9 mass % or less, particularly if high temperature
heat treatment is employed during fabrication, because stability
against reboiling further increases with the As.sub.2O.sub.3
content of 0.9 mass % or less. The As.sub.2O.sub.3 content is
preferably 0.6 mass % or less when another reboil gas component
coexists.
The glass composition according to the present invention is
intended for a multicomponent oxide glass consisting of a plurality
of oxide components of 1 mass % or more each, and the number of
oxide components which constitute a glass is desirably large. That
is, a three-component system rather than a two-component system, a
four-component system rather than a three-component system, and a
five-component system rather than a four-component system are
desirable respectively. Further, a six-, seven-component system or
more is generally more desirable. A larger number of components
generally reduces a melting temperature, thereby causing the
bubbles to float easily. On the other hand, an atomic distance
distribution among respective atoms in the molten glass consisting
of multicomponents becomes broader than that of the molten glass
consisting of a single component. As a result, sites of large
atomic distance exist in the molten glass, providing an effect of
easy diffusion of helium and neon in the molten glass.
Further, the glass composition of the present invention tends to
obstruct a diffusion pathway of helium or neon when components
having small atomic radii such as alkali metal elements are
included in the composition. Thus, an amount of the alkali metal
elements is desirably small. However, the alkali metal elements may
be added when the inclusion of the alkali metal elements is desired
in applications of the glass composition. Reduction in the
viscosity of the molten glass by addition of the alkali metal
elements promotes fining from the glass, thereby contributing to
improvements of the fining effect.
Hereinafter, the glass composition containing the alkali metal
elements will be described in detail.
A glass composition consisting of four or more oxide components and
allowing a very small content of alkali metal element additives,
for example, can be defined as follows.
That is, a glass composition manufactured by melting of glass raw
materials and containing four or more oxide components as main
components characterized by including: helium and/or neon in the
above-described range; a fining component in the above-described
range, as required; and alkali metal oxide elements such as
Li.sub.2O, Na.sub.2O, and K.sub.2O , so that the total content of
the elements is 10 mass ppm or more and less than 0.3 mass %.
The alkali metal oxide elements reduce the viscosity of the molten
glass. Reduction of the viscosity of the molten glass facilitates
degassing by fining from the molten glass. To realize the effect
even slightly, the total content of the alkali metal oxide elements
must be 10 mass ppm or more. To enhance the effect, the total
content of the alkali metal oxide elements is preferably 50mass ppm
or more. On the other hand, the alkali metal oxide elements may be
reduced to minimum depending on an environment where the glass is
used.
Alkali metals are desirably avoided as much as possible in sheet
glass for a liquid crystal substrate used for electronic parts or
the like, for example. For such an application, an upper limit of
the total content of the alkali metal oxide elements is 0.3 mass %.
Further, the total content of the alkali metal oxide elements is
desirably less than 0.1 mass % if the requirements of the
application are more demanding.
On the other hand, a glass composition capable of containing more
alkali metal elements can be defined as follows.
That is, a glass composition manufactured by melting of glass raw
materials and containing four or more oxide components as main
components characterized by including: helium and/or neon in the
above-described range; a fining agent component in the
above-described range, as required; and alkali metal oxides such as
Li.sub.2O, Na.sub.2O, and K.sub.2O , so that the total content of
the elements is 0.3 mass % or more and less than 16 mass %.
The glass composition used in applications allowing alkali metal
oxide elements may contain alkali metal oxide elements in an amount
of 0.3mass % or more as a total content, for further assuring the
effects such as viscosity reduction of the molten glass. The total
content of the alkali metal oxide elements is preferably 1.0 mass %
or more, for realizing a more assured effect. On the other hand,
basic physical properties of a glass exhibiting chemical resistance
such as suppression of alkali elution may deteriorate by the
addition of the alkali metal oxide elements, particularly with a
relatively simple oxide of about four components. Thus, an upper
limit of the total content of the alkali metal oxide elements is
preferably less than 16mass %, in applications requiring chemical
resistance. The upper limit must be further reduced to preferably
less than 10mass % for a poor use environment of the glass
composition.
A glass composition containing, for example, six or more oxide
components can be defined as follows.
That is, a glass composition manufactured by melting of glass raw
materials and containing six or more oxide components as main
components characterized by including: helium and/or neon in the
above-described range; a fining component in the above-described
range, as required; and alkali metal oxides such as Li.sub.2O,
Na.sub.2O, and K.sub.2O , so that the total content of the elements
is 16 mass % or more and less than 30 mass %.
As described above, the alkali metal oxide elements break the
network in the glass structure and reduce the viscosity of the
molten glass. Further, six or more oxide components constituting a
glass facilitates diffusion of helium and/or neon in the molten
glass. Thus, the glass composition consisting of six or more oxide
components enables an improvement of a fining effect by combining
the effect of reducing the viscosity of the molten glass and the
effect of promoting the diffusion of helium and/or neon without
restriction from the applications. Further, six or more oxide
components constituting a glass provide a better effect of chemical
resistance such as suppressing alkali elution by mutual combination
of oxide components. Thus, the total content of the alkali metal
oxide elements is preferably 16 mass % or more. On the other hand,
too large a total content of the alkali metal oxide elements causes
problems such as water resistance. Thus, the upper limit of the
total content of the alkali metal oxide elements is preferably 30
mass % or less. The upper limit of the total content of the alkali
metal oxide elements is preferably 20 mass % or less, particularly
for a glass composition used in a poor environment.
Further, the glass composition of the present invention can
appropriately contain: colorants such as transition metal element
compounds, rare earths, Au, Ag, Cu, sulfides, tellurium compounds,
and selenium compounds, exhibiting color with various colored ions,
additives causing colloid coloring such as a CdS--CdSe solid
solution, and radiation coloring additives such as Mn and Ce; and
additives of scarce metal elements for adjusting refractive index.
In contrast, elements such as U, Th, Fe, Ti, Pb, As, Cl, K, Cu, V,
Cr, Mn, Pt, Mo, and Zr may be finely controlled as appropriate to a
ppm order or a ppb order so that the glass composition contains a
minimal amount of the elements to meet the requirements of the
applications.
Of those, particularly Pt (platinum) may serve as a nucleus for
bubble formation during foaming in the molten glass through
intentional slight addition thereof, and is an effective component
for promptly producing bubbles for assured fining. The amount of Pt
addition is preferably 1 ppb or more, more preferably 50 ppb or
more. On the other hand, an upper limit of the amount of Pt
addition is preferably 50 ppm or more because an increased Pt
content often adversely affects optical properties or appearance
qualities. The upper limit of the amount of Pt addition is
preferably 30 ppm in applications particularly requiring optical
properties.
Further, the glass composition of the present invention may be
manufactured by melting in a heat resistant material containing Pt
As light amount of Pt intentionally added also provides an effect
of reducing Pt elution from the heat resistant metal material,
thereby preventing loss of glass homogeneity by formation of
contaminants containing the eluted Pt in the molten glass or
preventing color change of the glass by the eluted Pt.
Further, Mo (molybdenum) also may serve as a nucleus for bubble
formation in the glass composition containing helium and/or neon,
similar to Pt. A slight amount of Mo may be added in place of Pt,
if not posing problems in properties of the glass composition.
However, the effect of Mo is not as high as that of Pt, and thus,
the amount of Mo addition is preferably 5 ppm or more. The amount
of Mo addition is preferably 50 ppm or more for further assuring
the effect by Mo addition. The amount of Mo addition can be
increased to 1,000 ppm if not posing problems in optical uses. A
preferable upper limit of the amount of Mo addition is 700 ppm.
Further, a slight amount of Zr (zirconium) added as ZrO.sub.2
provides an effect of aiding diffusion of helium and/or neon in the
molten glass by being coexistent with helium and/or neon. ZrO2 may
be added in an amount of 5 ppm or more as Zr. Further, the amount
of zrO.sub.2addition is preferably 50 ppm or more, for assuredly
exhibiting the effect. On the other hand, an upper limit of the
amount of ZrO.sub.2 addition is preferably 5 mass % because
ZrO.sub.2 may increase the viscosity of the molten glass to
obstruct the diffusion of helium and/or neon. Further, the upper
limit of the amount of ZrO.sub.2 addition may be 3 mass % if
viscosity increase of the molten glass must be avoided.
The glass composition of the present invention can have a
previously designed material composition enabling precipitation of
a plurality of microcrystalline precipitates inside a glass body
through reheat treatment and energy transfer such as laser
irradiation.
Further, the glass composition of the present invention can cope
with various manufacture conditions according to applications
including: ion exchange treatment for imparting necessary optical
properties, strength properties, or the like; provision of various
thin films to a glass surface; implantation of specific ions to the
glass surface; surface treatment with chemicals or the like for
improving surface properties; solidification of radioactive
substances or the like; rapid-quenching vitrification using liquid
nitrogen, liquid helium, or the like; glass manufacture by
ultra-high temperature melting using solar energy; special glass
manufacture using a phenomenon of crystallization under ultra-high
pressure conditions; and inclusion of specific additives for
imparting other special electromagnetic properties.
DESCRIPTION OF PREFERRED EXAMPLES
Hereinafter, examples of the present invention will be
described.
Example 1
Samples No. 1 to No. 10 in Table 1 represent glass compositions
according to Example 1 of the present invention. A molten glass
melted in advance to yield a predetermined composition was poured
out onto a carbon plate, and a part thereof was subjected to
chemical composition analysis using an ICP emission spectroscopy or
the like. After the composition was determined, the molten glass
was pulverized to a particle size of 0.5 to 2.0 mm using an alumina
mortar. 50 g of the pulverized glass was poured into a platinum
crucible. The crucible was placed in an atmosphere furnace of an
airtight structure heated to 1,400.degree. C. in advance, and was
retained therein for 10 minutes. Then, helium (hereinafter,
referred to as He) or neon (hereinafter, referred to as Ne), each
adjusted to an appropriate concentration with nitrogen was
introduced into the furnace as an atmospheric gas for 30-minute
treatment. The ICP emission spectrometer used for chemical
composition analysis (SPS1500VR, manufactured by Seiko Instruments
Inc.) was equipped with secondary electron multiplier (SEM) for
improved measurement sensitivity. One analysis required about 0.5 g
of the glass. Note that, samples No. 1 to No. 10 in Table 1
correspond to the invention according to claim 1.
TABLE-US-00001 TABLE 1 Sample No. 1 2 3 4 5 6 7 8 9 10 (mass %)
SiO.sub.2 63.2 63.2 63.2 63.5 63.3 63.0 63.2 63.0 62.8 62.9
Al.sub.2O.sub.3 2.0 2.0 2.0 1.9 2.0 2.3 2.0 2.3 2.0 2.1 SrO 9.1 9.1
9.1 10.2 9.1 9.0 9.1 9.1 9.1 9.5 BaO 8.9 8.9 8.9 8.7 8.9 8.9 8.9
8.9 8.4 7.8 Na.sub.2O 7.6 7.6 7.6 7.5 7.6 7.6 7.6 7.9 7.6 6.9
K.sub.2O 7.7 7.7 7.7 8.2 7.6 7.7 7.7 7.8 8.8 9.2 ZrO.sub.2 1.5 1.5
1.5 0.0 1.5 1.5 1.5 1.0 1.3 1.6 (.mu.L/g) He 0.010 0.020 0.012
0.150 1.020 1.481 1.980 <0.001 0.003 0.451 Ne <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 1- .980
0.071 1.033 Number of bubbles 710 620 40 8 4 ND ND ND 350 8
(bubbles/10 g)
Further, composition analysis after remelting confirmed that oxide
compositions were the same as those before melting. The number of
bubbles remaining in the glass was determined using a stereoscopic
microscope of 20 to 100 power magnification while keeping the glass
in an immersion liquid having the same refractive index as the
glass. A He or Ne content was measured using a quadrupole mass
spectrometer (QMA125, manufactured by Balzers AG) equipped with a
secondary electron multiplier (SEM) for improved measurement
sensitivity. Gas analysis using the quadrupole mass spectrometer
involved: placing a glass sample to be measured in a platinum dish,
keeping the platinum dish in a sample chamber to a vacuum of
10.sup.-5 Pa (that is, 10.sup.-8 Torr); and introducing a gas
heated and discharged into the quadrupole mass spectrometer having
a measurement sensitivity of 0.001 .mu.L/g.
In Table 1, ND indicates that the sample could not be detected. The
results of the investigation confirmed that all glass contained He
and Ne. Further, the number of remaining bubbles confirmed that all
samples had qualities for commercialization as glass
compositions.
Comparative Example 1
Samples No. 11 to No. 20 in Table 2 represent glass compositions
according to Comparative Example 1 of the present invention. Molten
glass were prepared in the same manner as in Example 1, and samples
No. 11 to No. 20 in Comparative Example 1 were produced by
remelting in the same manner as in Example 1 except that the
melting atmosphere was changed to an atmospheric condition.
TABLE-US-00002 TABLE 2 Sample No. 11 12 13 14 15 16 17 18 19 20
(mass %) SiO.sub.2 63.2 63.2 63.2 63.5 63.3 63.0 63.2 63.0 62.8
62.9 Al.sub.2O.sub.3 2.0 2.0 2.0 1.9 2.0 2.3 2.0 2.3 2.0 2.1 SrO
9.1 9.1 9.1 10.2 9.1 9.0 9.1 9.1 9.1 9.5 BaO 8.9 8.9 8.9 8.7 8.9
8.9 8.9 8.9 8.4 7.8 Na.sub.2O 7.6 7.6 7.6 7.5 7.6 7.6 7.6 7.9 7.6
6.9 K.sub.2O 7.7 7.7 7.7 8.2 7.6 7.7 7.7 7.8 8.8 9.2 ZrO.sub.2 1.5
1.5 1.5 0.0 1.5 1.5 1.5 1.0 1.3 1.6 (.mu.L/g) He <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 &-
lt;0.001 <0.001 <0.001 Ne <0.001 <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 &- lt;0.001 <0.001
<0.001 Number of bubbles 1,320 870 1,060 2,570 1,850 890 950 790
880 780 (bubbles/10 g)
As a result, the number of bubbles of the samples in Example 1 in
Table 1 ranged from 72 bubbles/10 g to ND, while the number of
bubbles of the samples in Comparative Example 1 in Table 2 ranged
from 780 to 2,570 bubbles/10 g. The results confirmed that the
samples in Comparative Example 1 had many bubbles having a
micron-order bubble size and that the fining effect was not
provided at all. A slight content of He or Ne of less than 0.001
.mu.L/g was detected by contamination from air or the like without
intentional addition. However, such a slight content hardly
provides a significant effect as the present invention.
Example 2
Samples No. 21 to No. 90 in Tables 3 to 9 represent glass
compositions according to Example 2 of the present invention. The
glass compositions were prepared to contain fining components and
were melted in the same manner as in Example 1. Steam bubbling was
employed during melting for the glass compositions requiring a
large water content. The melted samples were subjected to He and Ne
analysis, and measurement of number of bubbles. Samples No. 21 to
30 in Table 3 correspond to the inventions according to claims 1 to
3. Further, sample No. 21 corresponds to the invention according
claim 6; samples No. 24 and No. 28 correspond to the invention
according to claim 4; sample No. 25 corresponds to the invention
according to claim 9; sample No. 26 corresponds to the invention
according to claim 8; sample No. 27 corresponds to the invention
according to claim 7; and samples No. 23 and No. 30 correspond to
the invention according to claim 5.
TABLE-US-00003 TABLE 3 Sample No. 21 22 23 24 25 26 27 28 29 30
(mass %) SiO.sub.2 64.2 64.2 64.2 63.5 63.3 62.7 63.1 64.0 62.8
63.0 Al.sub.2O.sub.3 2.0 2.5 2.5 1.9 3.5 2.3 3.5 2.3 2.0 2.0 SrO
9.1 9.1 9.1 10.2 9.1 10.5 9.1 8.9 9.1 9.1 BaO 8.9 8.2 8.8 8.7 8.9
8.9 8.9 8.9 8.4 8.9 Na.sub.2O 7.6 7.6 7.6 7.3 7.6 7.6 7.6 7.9 7.6
7.6 K.sub.2O 7.7 7.7 7.7 8.2 7.4 7.7 7.7 7.8 8.8 7.7 ZrO.sub.2 --
-- -- -- -- -- -- -- 1.3 1.5 Cl 0.5 -- -- -- -- -- -- -- -- -- F --
0.7 -- -- -- -- -- -- -- -- SO.sub.3 -- -- 0.1 -- -- -- -- -- --
0.2 Sb.sub.2O.sub.3 -- -- -- 0.2 -- -- -- 0.2 -- -- As.sub.2O.sub.3
-- -- -- -- 0.2 -- -- -- -- -- SnO.sub.2 -- -- -- -- -- 0.3 -- --
-- -- H.sub.2O -- -- -- -- -- -- 0.06 -- -- -- (.mu.L/g) He 1.200
1.503 1.201 1.005 0.906 1.500 1.006 1.100 0.452 0.421 Ne <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 0.303 0.012-
<0.001 <0.001 Number of bubbles 7 4 ND ND 0.03 ND ND ND 4 ND
(bubbles/10 g)
In Table 4, samples No. 31 to No. 34 and No. 39 correspond to the
inventions according to claims 1 to 3 and claim 6; and samples No.
35 to No. 38 and No. 40 correspond to the inventions according to
claim 1, claim 2, and claim 3.
TABLE-US-00004 TABLE 4 Sample No. 31 32 33 34 35 36 37 38 39 40
(mass %) SiO.sub.2 63.2 64.2 64.2 63.0 63.5 62.1 63.1 64.0 62.8
63.1 Al.sub.2O.sub.3 2.0 2.5 2.5 1.9 3.5 2.3 3.5 2.3 2.6 2.7 SrO
9.1 9.8 9.1 10.2 9.1 10.5 9.1 8.6 9.1 9.5 BaO 8.9 8.2 8.8 8.3 8.9
7.9 9.0 8.9 8.4 8.3 Na.sub.2O 7.6 7.6 7.6 7.3 7.6 7.6 7.6 6.9 7.6
6.6 K.sub.2O 7.7 7.7 7.8 8.2 7.4 7.7 7.7 7.8 8.8 9.2 ZrO.sub.2 --
-- -- -- -- -- -- -- -- -- Cl 1.5 0.03 0.02 1.1 -- -- -- -- 0.7 --
F -- -- -- -- 0.04 1.9 0.02 1.5 -- 0.6 SO.sub.3 -- -- -- -- -- --
-- -- -- -- Sb.sub.2O.sub.3 -- -- -- -- -- -- -- -- -- --
As.sub.2O.sub.3 -- -- -- -- -- -- -- -- -- -- SnO.sub.2 -- -- -- --
-- -- -- -- -- -- H.sub.2O -- -- -- -- -- -- -- -- -- -- (.mu.L/g)
He 0.430 0.782 0.650 0.553 0.524 0.531 0.725 0.683 0.990 1.652 Ne
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.032
0.010- 0.211 <0.001 Number of bubbles 4 8 8 4 ND ND ND ND ND ND
(bubbles/10 g)
Samples No. 41 to No. 50 in Table 5 correspond to the inventions
according to claims 1 to 3 and claim 5. Further, sample No. 44 and
sample No. 47 correspond to the inventions according to claim 11
and claim 8, respectively.
TABLE-US-00005 TABLE 5 Sample No. 41 42 43 44 45 46 47 48 49 50
(mass %) SiO.sub.2 64.3 64.2 64.2 63.0 63.5 62.3 63.0 64.1 63.1
62.9 Al.sub.2O.sub.3 2.3 2.5 2.4 1.9 3.4 2.3 3.5 2.3 2.6 3.6 SrO
8.8 9.8 9.1 10.3 9.1 11.3 9.1 8.6 9.1 9.5 BaO 8.9 8.2 8.8 8.3 8.9
7.9 9.0 9.0 8.4 7.8 Na.sub.2O 7.8 7.6 7.6 7.7 7.6 7.6 7.6 6.9 7.6
6.6 K.sub.2O 7.9 7.7 7.8 8.2 6.8 7.7 7.3 7.9 8.8 9.2 ZrO2 -- -- --
-- -- -- -- 0.9 -- -- Cl -- -- -- 0.1 -- -- -- -- -- -- F -- -- --
-- -- -- -- -- -- -- SO.sub.3 0.006 0.02 0.08 0.42 0.79 0.928 0.35
0.28 0.45 0.44 Sb.sub.2O.sub.3 -- -- -- -- -- -- -- -- -- --
As.sub.2O.sub.3 -- -- -- -- -- -- -- -- -- -- SnO.sub.2 -- -- -- --
-- -- 0.2 -- -- -- H.sub.2O -- -- -- -- -- -- -- -- -- -- (.mu.L/g)
He 0.430 0.782 0.643 0.553 0.525 0.531 0.724 0.683 0.991 1.655 Ne
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.030
0.011- 0.210 <0.001 Number of bubbles 7 7 6 ND ND ND ND ND ND ND
(bubbles/10 g)
Samples No. 51 to No. 60 in Table 6 correspond to the inventions
according to claims 1 to 3 and claim 4. Further, sample No. 53 and
sample No. 57 correspond to the inventions according to claim 6 and
claim 7, respectively.
TABLE-US-00006 TABLE 6 Sample No. 51 52 53 54 55 56 57 58 59 60
(mass %) SiO.sub.2 64.3 64.2 64.2 63.0 63.5 62.3 63.0 64.1 63.1
62.9 Al.sub.2O.sub.3 2.3 2.4 2.3 1.9 3.4 2.3 3.5 2.3 2.6 3.6 SrO
8.8 9.8 9.1 10.3 8.4 11.4 9.0 8.3 9.1 9.5 BaO 8.9 8.2 8.4 8.3 8.9
7.9 9.0 9.0 8.3 7.8 Na.sub.2O 7.8 7.6 7.6 6.8 7.6 7.6 7.6 6.9 7.6
6.6 K.sub.2O 7.9 7.7 7.8 8.2 6.8 7.7 7.3 7.9 8.8 9.3 ZrO.sub.2 --
-- -- -- -- -- -- 0.9 -- -- Cl -- -- 0.1 -- -- -- -- -- -- -- F --
-- -- -- -- -- -- -- -- -- SO.sub.3 -- -- -- -- -- -- -- -- -- --
Sb.sub.2O.sub.3 0.02 0.1 0.5 1.45 1.5 0.8 0.65 0.57 0.55 0.32
As.sub.2O.sub.3 -- -- -- -- -- -- -- -- -- -- SnO.sub.2 -- -- -- --
-- -- -- -- -- -- H.sub.2O -- -- -- -- -- -- 0.02 -- -- --
(.mu.L/g) He 0.431 0.765 0.644 0.586 0.524 0.530 0.724 0.683 0.982
1.387 Ne <0.001 <0.001 <0.001 <0.001 <0.001
<0.001 0.062 0.020- 0.226 <0.001 Number of bubbles 8 7 3 ND
ND ND ND ND ND ND (bubbles/10 g)
Samples No. 61 to No. 70 in Table 7 correspond to the inventions
according to claims 1 to 3 and claim 9. Further, sample No. 65
corresponds to the invention according to claim 7; sample No. 66
corresponds to the invention according to claim 5; and sample No.
67 corresponds to the inventions according claim 4 and claim
12.
TABLE-US-00007 TABLE 7 Sample No. 61 62 63 64 65 66 67 68 69 70
(mass %) SiO.sub.2 64.3 64.2 64.2 63.3 64.2 62.3 63.0 64.2 63.1
62.8 Al.sub.2O.sub.3 2.3 2.4 2.3 1.9 3.4 2.3 3.4 2.3 2.6 3.5 SrO
8.8 9.8 9.1 10.0 8.4 11.4 9.1 8.6 9.2 9.5 BaO 8.9 8.3 8.4 8.3 9.0
7.9 9.1 9.2 8.3 7.7 Na.sub.2O 7.8 7.6 7.6 6.8 7.6 7.7 7.6 6.9 7.6
6.6 K.sub.2O 7.9 7.7 7.5 8.2 6.8 7.9 7.3 7.9 8.8 9.3 ZrO.sub.2 --
-- -- -- -- -- -- 0.7 -- -- Cl -- -- -- -- -- -- -- -- -- -- F --
-- -- -- -- -- -- -- -- -- SO.sub.3 -- -- -- -- -- 0.02 -- -- -- --
Sb.sub.2O.sub.3 -- -- -- -- -- -- 0.11 -- -- -- As.sub.2O.sub.3
0.02 0.05 0.95 1.42 0.63 0.51 0.33 0.21 0.43 0.68 SnO.sub.2 -- --
-- -- -- -- -- -- -- -- H.sub.2O -- -- -- -- 0.11 -- -- -- -- --
(.mu.L/g) He 0.431 0.765 0.644 0.586 0.524 0.530 0.724 0.683 0.982
1.387 Ne <0.001 <0.001 <0.001 <0.001 <0.001
<0.001 0.061 0.048- 0.183 <0.001 Number of bubbles 8 6 3 ND
ND ND ND ND ND ND (bubbles/10 g)
Samples No. 71 to No. 80 in Table 8 correspond to the inventions
according to claims 1 to 3 and claim 8. Further, sample No. 74 and
sample No. 77 correspond to the inventions according to claim 6 and
claim 7, respectively.
TABLE-US-00008 TABLE 8 Sample No. 71 72 73 74 75 76 77 78 79 80
(mass %) SiO.sub.2 64.3 64.2 64.5 63.9 63.9 61.9 63.0 64.2 63.1
62.8 Al.sub.2O.sub.3 2.3 2.4 2.3 1.9 3.2 2.3 3.4 2.3 2.6 3.5 SrO
8.8 9.8 9.1 10.2 8.3 11.2 9.0 8.4 9.2 9.6 BaO 8.9 8.3 8.4 8.3 9.0
7.9 9.1 9.2 8.3 7.7 Na.sub.2O 7.8 7.6 7.6 6.8 7.7 7.7 7.6 6.9 7.6
6.6 K.sub.2O 7.9 7.7 7.5 8.2 6.5 7.9 7.2 7.9 8.8 9.3 ZrO.sub.2 --
-- -- -- -- -- -- 0.7 -- -- Cl -- -- -- 0.1 -- -- -- -- -- -- F --
-- 0.21 -- -- -- -- -- -- -- SO.sub.3 -- -- -- -- -- -- -- -- -- --
Sb.sub.2O.sub.3 -- -- -- -- -- -- -- -- -- -- As.sub.2O.sub.3 -- --
-- -- -- -- -- -- -- -- SnO.sub.2 0.001 0.057 0.451 0.682 1.502
1.201 0.563 0.351 0.411 0.562 H.sub.2O -- -- -- -- -- -- 0.06 -- --
-- (.mu.L/g) He 0.186 0.356 0.655 0.586 0.522 0.128 0.724 0.358
0.958 1.024 Ne <0.001 <0.001 0.002 <0.001 <0.001 0.211
0.021 0.039 0.180 &- lt;0.001 Number of bubbles 5 ND ND ND 3 ND
ND ND ND ND (bubbles/10 g)
Samples No. 81 to No. 90 in Table 9 correspond to the inventions
according to claims 1 to 3 and claim 7. Further, sample No. 83,
sample No. 86, and sample No. 88 correspond to the inventions
according to claim 4, claim 6, and claim 9, respectively.
TABLE-US-00009 TABLE 9 Sample No. 81 82 83 84 85 86 87 88 89 90
(mass %) SiO.sub.2 64.3 64.2 64.5 64.0 63.9 61.9 63.0 64.6 63.1
62.8 Al.sub.2O.sub.3 2.3 2.4 2.8 1.6 4.2 3.1 3.4 2.5 2.5 3.5 SrO
8.8 9.8 9.1 11.1 8.3 11.8 9.0 8.5 9.4 9.6 BaO 8.9 8.3 8.4 8.3 9.1
7.8 9.1 9.3 8.5 7.7 Na.sub.2O 7.8 7.6 7.6 6.5 7.9 7.6 7.7 6.9 7.6
6.6 K.sub.2O 7.9 7.7 7.5 8.1 6.5 7.7 7.2 7.9 9.0 9.8 ZrO.sub.2 --
-- -- 0.3 -- -- -- -- -- -- Cl -- -- -- -- -- 0.05 -- -- -- -- F --
-- -- -- -- -- 0.5 -- -- -- SO.sub.3 -- -- -- -- -- -- -- -- -- --
Sb.sub.2O.sub.3 -- -- 0.12 -- -- -- -- -- -- -- As.sub.2O.sub.3 --
-- -- -- -- -- -- 0.2 -- -- SnO.sub.2 -- -- -- -- -- -- -- -- -- --
H.sub.2O 0.01 0.03 0.09 0.08 0.14 0.11 0.1 0.11 0.07 0.06 (.mu.L/g)
He 0.211 0.523 0.662 0.556 0.534 0.539 0.754 0.658 0.945 1.325 Ne
<0.001 <0.001 <0.001 0.010 <0.001 <0.001 0.061 0.033
0.1- 70 <0.001 Number of bubbles 9 6 3 ND ND ND ND ND ND ND
(bubbles/10 g)
Tables 3 to 9 confirmed that each of samples No. 21 to No. 90 in
Example No. 2 contained a predetermined amount or more of He and Ne
in total and had a small number of bubbles.
Comparative Example 2
Samples No. 91 to No. 100 in Table 10 represent glass compositions
according to Comparative Example 2 of the present invention. Molten
glass were prepared in the same manner as in Example 2, and samples
No. 91 to 100 in Comparative Example 2 were produced by remelting
in the same manner as in Example 2 except that the melting
atmosphere was changed to an atmospheric condition.
TABLE-US-00010 TABLE 10 Sample No. 91 92 93 94 95 96 97 98 99 100
(mass %) SiO.sub.2 64.2 64.2 64.2 63.5 63.3 62.7 63.1 64.0 62.8
62.9 Al.sub.2O.sub.3 2.0 2.5 2.5 1.9 3.5 2.3 3.5 2.3 2.0 2.8 SrO
9.1 9.1 9.1 10.2 9.1 10.5 9.1 8.9 9.1 9.5 BaO 8.9 8.2 8.8 8.7 8.9
8.9 8.9 8.9 8.4 7.8 Na.sub.2O 7.6 7.6 7.6 7.3 7.6 7.6 7.6 7.9 7.6
6.6 K.sub.2O 7.7 7.7 7.7 8.2 7.4 7.7 7.7 7.8 8.8 9.2 ZrO.sub.2 --
-- -- -- -- -- -- -- 1.3 -- Cl 0.5 -- -- -- -- -- -- -- -- 1.2 F --
0.7 -- -- -- -- -- -- -- -- SO.sub.3 -- -- 0.1 -- -- -- -- -- --
Sb.sub.2O.sub.3 -- -- -- 0.2 -- -- -- 0.2 -- -- As.sub.2O.sub.3 --
-- -- -- 0.2 -- -- -- -- -- SnO.sub.2 -- -- -- -- -- 0.3 -- -- --
-- H.sub.2O -- -- -- -- -- -- 0.06 -- -- -- (.mu.L/g) He <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 &-
lt;0.001 <0.001 <0.001 Ne <0.001 <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 &- lt;0.001 <0.001
<0.001 Number of bubbles 520 350 440 100 220 590 1,020 350 550
1,210 (bubbles/10 g)
The samples in Comparative Example 2 contain fining components, and
thus, the number of bubbles in the samples is reduced compared to
the samples without the fining agent. However, the samples in
Comparative Example 2 had more bubbles than the samples containing
He and Ne in Example 2.
Example 3
Samples No. 101 to No. 110 in Table 11 represent glass compositions
according to Example 3 of the present invention. A molten glass
melted in a He (99.9999% purity) melting atmosphere at
1,400.degree. C. for 40 minutes in advance to yield a predetermined
composition was poured out onto a carbon plate, and a part thereof
was subjected to chemical composition analysis. After the
composition was determined, the molten glass was pulverized to a
particle size of 0.2 to 0.5 mm using an alumina mortar. 50 g of the
pulverized coarse-grained glass was poured into a platinum
crucible. The crucible was placed in an atmosphere furnace of an
airtight structure heated to 1,500.degree. C. in advance, retained
therein for 10 minutes for remelting, and taken out. After cooling,
composition analysis after remelting confirmed that compositions
were the same as those before melting. The size of bubbles
remaining in the glass was determined using a stereoscopic
microscope of 20 to 100 power magnification while keeping the glass
in an immersion liquid having the same refractive index as the
glass.
Samples No. 101 to No. 110 in Table 11 correspond to the invention
according to claim 1; and samples No. 101 to No. 108 and No. 110
correspond to the inventions according to claims 2 and 3. Further,
sample No. 101 corresponds to the invention according to claim 6;
samples No. 103 and No. 110 correspond to the invention according
to claim 5; samples No. 104 and No. 108 correspond to the invention
according to claim 4; sample No. 105 corresponds to the invention
according to claim 9; sample No. 106 corresponds to the invention
according to claim 8; and sample No. 107 corresponds the invention
according to claim 7.
TABLE-US-00011 TABLE 11 Sample No. 101 102 103 104 105 106 107 108
109 110 (mass %) SiO.sub.2 64.1 64.3 64.2 63.5 63.2 62.8 63.3 63.8
62.8 63.0 Al.sub.2o.sub.3 2.0 2.5 2.6 2.0 3.5 2.3 3.5 2.5 2.2 2.0
SrO 9.2 9.1 9.1 10.2 9.1 10.5 9.1 8.9 9.1 9.1 BaO 8.9 8.1 8.8 8.7
9.0 8.8 8.9 8.9 8.4 8.9 Na.sub.2O 7.6 7.6 7.6 7.4 7.6 7.6 7.6 7.9
7.6 7.6 K.sub.2O 7.7 7.7 7.6 8.0 7.4 7.7 7.5 7.8 8.8 7.7 ZrO.sub.2
-- -- -- -- -- -- -- -- 1.1 1.5 Cl 0.5 -- -- -- -- -- -- -- -- -- F
-- 0.7 -- -- -- -- -- -- -- -- SO.sub.3 -- -- 0.1 -- -- -- -- -- --
0.2 Sb.sub.2O.sub.3 -- -- -- 0.2 -- -- -- 0.2 -- -- As.sub.2O.sub.3
-- -- -- -- 0.2 -- -- -- -- -- SnO.sub.2 -- -- -- -- -- 0.3 -- --
-- -- H.sub.2O -- -- -- -- -- -- 0.06 -- -- -- (.mu.L/g) He 1.120
1.495 1.235 1.102 0.985 1.480 1.002 1.098 0.348 0.421 Ne 0.003
<0.001 <0.001 <0.001 <0.001 <0.001 0.302 0.011
<0.001 <0.001 Average bubble size <0.1 <0.1 <0.1
<0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 (mm)
Comparative Example 3
Samples No. 111 to No. 120 in Table 12 represent glass compositions
according to Comparative Example 3 of the present invention. Molten
glass were prepared in the same manner as in Example 3, and samples
No. 111 to No. 120 in Comparative Example 3 were produced by
remelting in the same manner as in Example 3 except that the
melting atmosphere was changed to an atmospheric condition.
TABLE-US-00012 TABLE 12 Sample No. 111 112 113 114 115 116 117 118
119 120 (mass %) SiO.sub.2 64.1 64.3 64.2 63.5 63.2 62.8 63.3 63.8
62.8 63.0 Al.sub.2O.sub.3 2.0 2.5 2.6 2.0 3.5 2.3 3.5 2.5 2.2 2.0
SrO 9.2 9.1 9.1 10.2 9.1 10.5 9.1 8.9 9.1 9.1 BaO 8.9 8.1 8.8 8.7
9.0 8.8 8.9 8.9 8.4 8.9 Na.sub.2O 7.6 7.6 7.6 7.4 7.6 7.6 7.6 7.9
7.6 7.6 K.sub.2O 7.7 7.7 7.6 8.0 7.4 7.7 7.5 7.8 8.8 7.7 ZrO.sub.2
-- -- -- -- -- -- -- -- 1.1 1.5 Cl 0.5 -- -- -- -- -- -- -- -- -- F
-- 0.7 -- -- -- -- -- -- -- -- SO.sub.3 -- -- 0.1 -- -- -- -- -- --
0.2 Sb.sub.2O.sub.3 -- -- -- 0.2 -- -- -- 0.2 -- -- As.sub.2O.sub.3
-- -- -- -- 0.2 -- -- -- -- -- SnO.sub.2 -- -- -- -- -- 0.3 -- --
-- -- H.sub.2O -- -- -- -- -- -- 0.06 -- -- -- (.mu.L/g) He
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 Ne <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001
<0.001 <0.001 Average bubble size 0.80 1.00 0.86 0.92 0.78
0.86 0.68 0.58 0.85 0.49 (mm)
As a result, an average size of the bubbles remaining ranged from
0.49 mm to 1 mm for the samples in Comparative Example 3 subjected
to atmospheric treatment while the average size of the bubbles
remaining was 0.1 mm or less for the samples in Example 3 subjected
to He or Ne treatment. The results confirmed that reheat treatment
prevents reboiling.
Example 4
Samples No. 121 to No. 170 in Tables 13 to 17 represent glass
compositions according to Example 4 of the present invention. Of
those, samples No. 121 to No. 160 were produced by: pouring into a
platinum crucible a batch of about 500 g of glass prepared in
advance to yield a predetermined composition; placing the crucible
in an atmosphere furnace of an airtight structure heated to 1,
400.degree. C., 1,450.degree. C., 1,500.degree. C., and
1,550.degree. C. in advance, depending on the kind of glass
compositions, respectively; and retaining the crucible in the
furnace for 4 hours. Further, samples No. 161 to No. 170 in Table
17 were produced by melting in the same furnace at 1, 550.degree.
C. for 2 hours. Samples No. 121 to No. 160 were produced by:
placing a crucible containing glass in the furnace; retaining the
crucible therein for 4 hours; introducing an atmospheric gas having
95% or more He or Ne concentration into the furnace; and retaining
the crucible at a predetermined temperature for 30 minutes.
Further, samples No. 161 to No. 170 in Table 17 were produced
through treatment in a He atmosphere at 1,600.degree. C. for 2
hours. Then, each sample was taken out from the furnace and poured
out into a mold made of glassy carbon for molding. After cooling,
analysis after remelting confirmed that compositions were the same
as those before melting. The size of bubbles remaining in the glass
was determined using a stereoscopic microscope of 20 to 100 power
magnification while keeping the glass in an immersion liquid having
the same refractive index as the glass.
Samples No. 121 to No. 125 and No. 127 to No. 130 in Table 13
correspond to the inventions according to claims 1 to 3 and claim
4. Further, sample No. 126 corresponds to the inventions according
to claims 1 to 3 and claim 5.
TABLE-US-00013 TABLE 13 Sample No. 121 122 123 124 125 126 127 128
129 130 (mass %) SiO.sub.2 71.8 69.8 71.5 72.7 72.2 71.3 70.3 65.1
71.4 68.6 Al.sub.2O.sub.3 2.0 1.7 2.2 1.8 1.6 1.5 1.8 2.3 1.8 3.0
B.sub.2O.sub.3 -- 1.1 -- -- -- 1.2 1.0 1.6 2.5 1.0 MgO 4.5 3.1 3.0
2.7 2.6 3.2 3.7 5.6 4.8 3.7 CaO 4.3 6.1 5.6 4.7 5.4 5.1 4.8 5.4 3.9
4.2 BaO -- 0.4 -- -- -- -- -- -- -- 0.2 Na.sub.2O 16.1 15.8 15.6
16.4 16.9 16.8 15.9 16.5 12.9 17.1 K.sub.2o 0.8 1.3 1.4 1.2 0.8 0.9
1.3 2.1 1.3 1.1 P.sub.2O.sub.5 -- 0.2 0.2 -- -- -- 0.4 0.8 0.5 0.4
Fe.sub.2O.sub.3 -- 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 SO.sub.3 --
-- -- -- -- 0.15 0.2 0.1 0.3 0.2 Sb.sub.2O.sub.3 0.5 0.5 0.4 0.5
0.4 -- 0.6 0.5 0.6 0.5 (.mu.L/g) He 0.300 0.536 0.253 0.425 0.356
0.564 0.452 0.568 0.554 0.452 Ne <0.001 0.01 <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Number
of bubbles 1 2 1 1 1 ND ND ND ND 2 (bubbles/10 g)
Samples No. 131 to No. 140 in Table 14 correspond to the inventions
according to claims 1 to 3 and claim 4.
TABLE-US-00014 TABLE 14 Sample No. 131 132 133 134 135 136 137 138
139 140 (mass %) SiO.sub.2 63.1 60.6 61.0 60.6 60.9 63.1 64.0 62.4
51.9 46.6 Al.sub.2O.sub.3 2.0 1.9 2.0 1.9 3.6 3.3 1.8 2.1 4.5 3.7
MgO -- 0.3 0.4 0.3 0.9 0.7 -- -- 1.5 -- CaO -- 1.1 1.8 1.1 1.7 0.9
2.8 -- 3.6 1.5 SrO 9.1 7.9 7.6 8.1 2.5 6.9 9.2 8.9 0.9 2.3 BaO 8.9
8.9 9.1 9.1 12.5 8.4 2.1 8.6 1.1 0.1 ZnO -- -- -- -- 0.4 -- -- 0.5
-- -- PbO -- -- -- -- -- -- 2.9 -- -- 32.8 Li.sub.2O -- -- 0.2 --
-- -- -- -- 21.8 -- Na.sub.2O 7.6 7.8 7.5 7.6 8.2 9.0 8.0 7.8 6.1
2.7 K.sub.2O 7.6 8.1 7.0 7.9 7.9 7.1 7.9 7.9 8.1 9.9 CeO.sub.2 --
0.4 0.3 0.3 0.2 0.2 0.3 0.2 -- -- ZrO.sub.2 1.5 2.2 2.5 2.3 -- --
-- -- 0.2 -- TiO.sub.2 -- 0.5 0.4 0.5 0.6 0.1 0.4 0.6 0.1 --
Fe.sub.2O.sub.3 -- 0.05 0.03 0.06 0.04 0.05 0.05 0.05 0.07 0.05
Nd.sub.2O.sub.3 -- -- -- -- -- -- -- 0.4 -- -- F -- 0.09 0.02 0.02
-- 0.02 0.02 -- -- -- Sb.sub.2O.sub.3 0.2 0.25 0.3 0.25 0.5 0.4 0.5
0.3 0.15 0.4 (.mu.L/g) He 0.400 0.552 0.389 0.624 0.524 0.386 0.210
0.352 0.181 0.130 Ne <0.001 0.022 <0.001 <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 Number of bubbles
1 1 1 1 1 ND ND ND ND 2 (bubbles/10 g)
Samples No. 141, No. 143 to No. 146, and No. 148 in Table 15
correspond to the inventions according to claims 1 to 3 and 4.
Further, samples No. 142, No. 147, and No. 149 to No. 150
correspond to the invention according to claim 1; samples No. 143
and No. 146 correspond to the inventions according to claims 8 and
10; samples No. 149 and No. 150 correspond to the inventions
according to claims 2, 3, and 9; and samples No. 145 and No. 146
correspond to the inventions according to claims 9 and 12.
TABLE-US-00015 TABLE 15 Sample No. 141 142 143 144 145 146 147 148
149 150 (mass %) SiO.sub.2 71.9 54.6 59.9 67.5 67.8 60.9 69.9 70.4
55.3 55.8 Al.sub.2O.sub.3 7.0 14.0 15.1 22.0 22.2 13.5 5.3 1.9 11.0
11.5 B.sub.2O.sub.3 11.0 8.0 9.9 9.5 9.9 0.8 7.0 7.2 CaO 1.0 23.0
5.3 6.4 0.8 5.7 7.0 6.5 SrO 6.0 5.5 1.0 0.8 BaO 1.0 2.5 3.0 2.1 0.5
14.3 15.2 ZnO 0.5 0.5 3.6 2.6 MgO 0.4 0.4 2.8 Li.sub.2O 4.0 3.9
Na.sub.2O 6.0 0.3 0.5 0.5 5.9 16.0 K.sub.2O 2.0 0.1 0.3 0.3 2.5 1.4
P.sub.2O.sub.5 0.3 As.sub.2O.sub.3 0.5 0.5 0.8 0.4 ZrO.sub.2 0.2
2.1 2.0 0.1 Sno.sub.2 0.02 0.01 TiO.sub.2 2.0 1.9 3.0
Sb.sub.2O.sub.3 0.1 0.5 1.2 0.5 0.1 0.2 Fe.sub.2O.sub.3 0.6
(.mu.L/g) He 0.386 0.435 0.170 0.551 0.480 0.386 0.211 0.353 0.180
0.143 Ne <0.001 0.028 <0.001 <0.001 <0.001 <0.001
<0.001 <0- .001 <0.001 <0.001 Number of bubbles 1 ND 1
1 1 ND ND ND ND 2 (bubbles/10 g)
Samples No. 151 to No. 154, No. 156, and No. 158 to No. 160 in
Table 16 correspond to the inventions according to claims 1 to 3.
Further, sample No. 155 corresponds to the invention according to
claim 1; samples No. 151 and No. 160 correspond to the invention
according to claim 9; samples No. 152 and No. 158 to No. 160
correspond to the invention according to claim 4; sample No. 153
corresponds to the invention according to claim 6; and sample No.
160 corresponds to the invention according to claim 12.
TABLE-US-00016 TABLE 16 Sample No. 151 152 153 154 155 156 157 158
159 160 (mass %) SiO.sub.2 68.2 35.5 75.5 63.9 70.9 68.7 60.4 26.0
33.4 48.3 Al.sub.2O.sub.3 3.5 0.1 1.3 6.5 2.1 3.7 14.8
B.sub.2O.sub.3 18.5 16.3 21.0 0.9 1.0 1.2 3.1 CaO 0.4 0.4 0.5 0.1
SrO 0.7 1.0 0.2 BaO 5.8 7.4 5.0 PbO 58.9 71.7 55.0 37.0 Li.sub.2O
1.1 2.8 1.1 1.0 Na.sub.2O 0.4 4.1 6.6 4.1 10.4 15.9 0.5 8.0
K.sub.2O 8.3 5.1 1.6 1.5 9.4 4.2 2.4 0.5 2.0 6.0 As.sub.2O.sub.3
0.1 0.4 ZrO.sub.2 5.0 F 0.5 0.3 Cl 0.1 Sb.sub.2O.sub.3 0.4 0.6 0.5
0.2 Fe.sub.2O.sub.3 3.0 3.0 0.1 (.mu.L/g) He 0.241 0.189 0.170
0.222 0.527 0.250 0.221 0.356 0.180 0.111 Ne <0.001 0.020
<0.001 0.015 <0.001 <0.001 <0.001 <0.001- <0.001
<0.001 Number of bubbles ND ND 1 1 1 1 ND ND ND 2 (bubbles/10
g)
Samples No. 161 to No. 170 in Table 17 correspond to the inventions
according to claims 1 to 3. Further, samples No. 161 to No. 162,
No. 164 to No. 166, and No. 169 to No. 170 correspond to the
invention according to claim 4; samples No. 162 and No. 166
correspond to the invention according to claim 9; samples No. 161,
No. 164 to No. 165, and No. 169to No. 170 correspond to the
invention according to claim 8; samples No. 163 and No. 167 to No.
168 correspond to the invention according to claim 5; and samples
No. 163 to No. 164 and No. 167 to No. 168 correspond to the
invention according to claim 6. Further, samples No. 161, No. 164
to No. 165, and No. 169 to No. 170 correspond to the invention
according to claim 10; samples No. 163 and No. 167 to No. 168
correspond to the invention according to claim 11; and samples No.
162 and No. 166 correspond to the invention according to claim
12.
TABLE-US-00017 TABLE 17 Sample No. 161 162 163 164 165 166 167 168
169 170 (mass %) SiO.sub.2 59.8 59.9 59.7 59.3 59.5 59.8 58.9 59.4
58.2 60.0 Al.sub.2O.sub.3 14.9 15.1 15.5 14.9 14.9 14.8 15.1 14.8
15.1 14.9 B.sub.2O.sub.3 9.9 9.7 9.4 9.7 9.9 9.9 9.8 9.9 9.9 9.7
CaO 5.3 5.4 5.2 5.0 5.1 5.3 5.3 5.3 5.3 5.2 SrO 6.0 5.7 5.9 5.8 6.0
6.0 5.9 5.8 5.5 5.2 BaO 2.5 2.5 2.3 2.4 2.5 2.5 2.4 2.5 2.5 2.4 PbO
0.5 0.5 0.4 0.5 0.5 0.5 0.5 0.5 0.3 0.4 ZrO.sub.2 0.2 0.2 0.2 0.2
0.2 0.2 0.2 0.2 0.2 0.2 Sb.sub.2O.sub.3 1.0 0.3 1.0 0.8 0.5 1.3 0.9
As.sub.2O.sub.3 0.7 0.5 SnO.sub.2 0.2 0.2 0.6 1.7 1.1 SO.sub.3 0.4
0.7 0.8 Cl 1.0 1.0 1.2 0.8 (.mu.L/g) He 0.843 0.952 0.581 0.630
0.153 0.443 0.543 0.391 0.567 0.455 Ne <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 &- lt;0.001
<0.001 <0.001 Number of bubbles ND ND 10 2 ND 6 3 1 2 1
(bubbles/10 g)
Comparative Example 4
Samples No. 171 to No. 180 in Table 18 and samples No. 181 to No.
190 in Table 19 represent glass compositions according to
Comparative Example 4 of the present invention. Molten glass were
prepared in the same manner as in Example 4 of Table 16, and
samples No. 171 to No. 180 in Comparative Example 4 were produced
by remelting in the same manner as in Example 4 except that the
melting atmosphere was changed to an atmospheric condition. Molten
glass were prepared in the same manner as in Example 4 of Table 17,
and samples No. 181 to No. 190 in Comparative Example 4 were
produced by remelting in the same manner as in Example 4 except
that the melting atmosphere was changed to an atmospheric
condition. After cooling, analysis after remelting confirmed that
oxide compositions were the same as those before melting. The
number of bubbles remaining in the glass was determined using a
stereoscopic microscope of 20 to 100 power magnification while
keeping the glass in an immersion liquid having the same refractive
index as the glass.
TABLE-US-00018 TABLE 18 Sample No. 171 172 173 174 175 176 177 178
179 180 (mass %) SiO.sub.2 68.0 35.3 75.0 63.7 70.9 68.7 60.4 26.0
33.4 48.3 Al.sub.2O.sub.3 3.5 0.1 1.3 6.5 2.1 3.7 0.3
B.sub.2O.sub.3 18.6 16.5 21.2 0.9 1.0 1.2 3.1 CaO 0.5 0.4 0.5 0.1
SrO 0.7 1.0 0.2 BaO 5.8 7.4 5.0 PbO 59.1 71.7 55.0 37.0 Li.sub.2O
1.2 2.8 1.1 1.0 Na.sub.2O 0.4 4.2 6.6 4.1 10.4 15.9 0.5 8.0
K.sub.2O 8.3 5.1 1.7 1.5 9.4 4.2 2.4 0.5 2.0 6.0 As.sub.2O.sub.3
0.1 0.4 ZrO.sub.2 19.5 F 0.5 0.3 Cl 0.1 Sb.sub.2O.sub.3 0.4 0.6 0.5
0.2 Fe.sub.2O.sub.3 3.0 3.0 0.1 (.mu.L/g) He <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 &- lt;0.001
<0.001 <0.001 Ne <0.001 <0.001 <0.001 <0.001
<0.001 <0.001 <0.001 &- lt;0.001 <0.001 <0.001
Number of bubbles 280 690 1,240 750 670 420 1,020 1,640 1,630 1,010
(bubbles/10 g)
TABLE-US-00019 TABLE 19 Sample No. 181 182 183 184 185 186 187 188
189 190 (mass %) SiO.sub.2 59.8 59.9 59.7 59.3 59.5 59.8 58.9 59.4
58.2 60.0 Al.sub.2O.sub.3 14.9 15.1 15.5 14.9 14.9 14.8 15.1 14.8
15.1 14.9 B.sub.2O.sub.3 9.9 9.7 9.4 9.7 9.9 9.9 9.8 9.9 9.9 9.7
CaO 5.3 5.4 5.2 5.0 5.1 5.3 5.3 5.3 5.3 5.2 SrO 6.0 5.7 5.9 5.8 6.0
6.0 5.9 5.8 5.5 5.2 BaO 2.5 2.5 2.3 2.4 2.5 2.5 2.4 2.5 2.5 2.4 PbO
0.5 0.5 0.4 0.5 0.5 0.5 0.5 0.5 0.3 0.4 ZrO.sub.2 0.2 0.2 0.2 0.2
0.2 0.2 0.2 0.2 0.2 0.2 Sb.sub.2O.sub.3 1.0 0.3 1.0 0.8 0.5 1.3 0.9
As.sub.2O.sub.3 0.7 0.5 SnO.sub.2 0.2 0.2 0.6 1.7 1.1 So.sub.3 0.4
0.7 0.8 Cl 1.0 1.0 1.2 0.8 (.mu.L/g) He <0.001 <0.001
<0.001 <0.001 <0.001 <0.001 <0.001 &- lt;0.001
<0.001 <0.001 Ne <0.001 <0.001 <0.001 <0.001
<0.001 <0.001 <0.001 &- lt;0.001 <0.001 <0.001
Number of bubbles 810 110 1,630 750 6,230 5,830 480 280 160 4,830
(bubbles/10 g)
The results of direct melting the raw materials confirmed that the
samples in Example 4 containing He and Ne had no bubbles or, if
any, about 1 to 2 bubbles/10 g after cooling. On the other hand,
the samples in Comparative Example 4 without He and Ne had about
110 to 6,230 bubbles/10 g, which is an apparently larger number
than that in Example 4. That is, the number of bubbles is reduced
by including He and Ne in the glass composition.
Example 5
Glass raw materials were prepared to yield a glass composition
shown in Table 20. Then, 500 g of the glass raw materials was
charged into a platinum-rhodium (15%) crucible for glass melting.
The crucible was placed in an indirect electric resistance furnace
for melting at 1,500.degree. C. for 3 hours. A He gas (99.9999%
purity) was introduced into the furnace through a supply port
connected to the inside of the electric resistance furnace during
melting. Melting was conducted while confirming complete
replacement of the furnace atmosphere with He from analysis results
of N.sub.2, CO.sub.2, CO, Ar, and O.sub.2 in exhaust. After melting
for a predetermined period of time, the molten glass was cast in a
carbon mold, and cooled in a slow cooling furnace. Then, an amount
required for analysis was sampled. A Pt (platinum) content in the
molded glass was analyzed using an ICP mass spectrometer similar to
the above-described analyzer (7000S, manufactured by Agilent
Technologies, Inc.). The results show that the glass contains 3.1
ppm of platinum eluted from an inner wall of the crucible used for
melting.
TABLE-US-00020 TABLE 20 Sample No. 191 (mass %) SiO.sub.2 63.2
Al.sub.2O.sub.3 2.0 SrO 9.1 BaO 8.9 Na.sub.2O 7.6 K.sub.2O 7.7
ZrO.sub.2 1.5
Comparative Example 5
The same glass raw materials as those of Example 5 were melted in
two melting atmospheres (atmospheric condition and N.sub.2
(nitrogen atmosphere)) at 1,500.degree. C. for 3 hours using the
same apparatus as in Example 5. AN.sub.2 (nitrogen) gas, similar to
He, was supplied through a supply port connected to the inside of
the electric resistance furnace. A Pt (platinum) content in the
molded glass was analyzed in the same manner as in Example 5 using
an ICP mass spectrometer. The results show the Pt content of 4.1
ppm in the glass produced by melting in a N.sub.2 atmosphere, and
the Pt content of 5.1 ppm in the glass produced by melting in an
atmospheric condition, both indicating large amounts of Pt melted
in the glass.
As described above, glass melting in a He atmosphere enables
reduction of an amount of Pt melting into the molten glass and
suppresses the Pt content in the glass product even when glass is
melted in an environment containing platinum, to thereby provide
homogeneous glass product.
Example 6
A discharge rate of a gas discharged from the molten glass by
introduction of a He gas was studied, to investigate how He
functions in the molten glass.
Table 21 shows a glass composition used for the investigation. 1 g
of glass melted and analyzed for its composition in advance was
held in a platinum boat, and the boat was placed inside an electric
furnace of an airtight structure. The boat was heated in an
environment of nitrogen and He introduced as carrier gases, and the
discharge rate of the gas discharged was measured. The discharge
rate of the gas discharged was measured using a quadrupole mass
spectrometer. Table 22 shows the results.
TABLE-US-00021 TABLE 21 Sample No. 192 193 (mass %) SiO.sub.2 63.0
58.9 Al.sub.2O.sub.3 2.0 14.1 B.sub.2O.sub.3 -- 9.8 CaO -- 5.2 SrO
9.1 5.9 BaO 8.9 2.4 ZnO -- 0.5 Na.sub.2O 7.6 -- K.sub.2O 7.7 --
ZrO.sub.2 1.5 0.2 SO.sub.3 0.2 -- Sb.sub.2O.sub.3 -- 1.0
As.sub.2O.sub.3 -- 1.0 SnO.sub.2 -- 1.0
TABLE-US-00022 TABLE 22 Sam- Gas discharge rate (.mu.L/g sec) ple
Measurement Measurement at 0.degree. C., 1 atm No. gas species
temperature N.sub.2 carrier gas He carrier gas 192 SO.sub.2 1550
0.01 0.10 193 O.sub.2 1300 0.03 0.70 O.sub.2 1400 0.04 0.70 O.sub.2
1600 0.02 0.80
Samples No. 192 and No. 193 have different compositions and use
different fining agents. Table 22 clearly shows that the discharge
rates of the gas discharged from both samples by the introduction
of the He gas as a carrier gas are about 10 times the discharge
rates of the gas discharged by N.sub.2 introduction and are
independent of temperature. The gas discharge rate is in direct
proportion with an inner partial pressure of the gas in the molten
glass. A large inner partial pressure of the molten glass can be
indirectly grasped through He introduction.
The glass composition according to the present invention is
manufactured by melting the glass raw materials, contains a
plurality of oxides as main components, and contains a
predetermined amount of helium and/or neon in the molten glass.
Thus, bubbles hardly remain in the glass as defects, and the glass
composition is highly homogeneous. Therefore, prosperity can be
further promoted in a variety of industries employing diverse glass
products.
Further, the inclusion of the fining component enables assured
clarifying of the glass during melting while imparting properties
of inhibiting reboiling by heat treatment or the like to the glass
product. Therefore, further exploitation of applications can be
promoted in industrial fields employing the glass products.
* * * * *